Signal Demodulation Method and Device

1. A signal demodulation method, comprising: obtaining, by a parameter obtaining unit, a receive signal; obtaining, by the parameter obtaining unit, a symbol probability parameter of the receive signal, wherein the symbol probability parameter comprises: amplitude r y and phase angle φ y of the receive signal, amplitude r x j and phase angle φ x j of each constellation point x j in a decision constellation point set, and a standard deviation σ n of Gaussian noise and a standard deviation σ θ of phase noise, wherein the decision constellation point set is located in a modulation constellation graph for performing signal demodulation; calculating, by a probability calculation unit, according to the symbol probability parameter, a symbol probability that a transmit signal corresponding to the receive signal is each constellation point x j in the decision constellation point set, wherein the calculating the symbol probability that the transmit signal corresponding to the receive signal is each constellation point x j in the decision constellation point set comprises calculating: Pr ⁡ ( x = x j / y ) = r y 4 ⁢ πσ n ⁢ exp ⁡ ( - ( r y - r x j ) 2 2 ⁢ σ n 2 - r x j ⁢ r y ⁡ ( φ y - φ x j ) 2 2 ⁢ ⁢ v j ) / v j wherein the v j =r x j r y σ θ 2 +σ n 2 and the Pr(x=x j /y) is the symbol probability; performing, by a demodulation processing unit, demodulation according to the symbol probability, and outputting demodulation information, wherein the demodulation information corresponds to a data bit corresponding to the transmit signal.

2. The signal demodulation method according to claim 1 , wherein the performing demodulation according to the symbol probability, and outputting demodulation information comprises: determining that a constellation point having a maximum symbol probability in the decision constellation point set is a constellation point corresponding to the transmit signal; and searching for a data bit corresponding to the constellation point, wherein the data bit is the data bit corresponding to the transmit signal, and outputting the data bit; wherein the demodulation information is the data bit corresponding to the transmit signal.

3. The signal demodulation method according to claim 1 , wherein the performing demodulation according to the symbol probability, and outputting demodulation information comprises: performing the demodulation according to the symbol probability, and outputting soft information, wherein the soft information comprises a symbol probability, a bit probability, a likelihood ratio, or a log-likelihood ratio; wherein the demodulation information is soft information used to generate the data bit corresponding to the transmit signal.

4. The signal demodulation method according to claim 3 , wherein the demodulation information is a likelihood ratio or a log-likelihood ratio, and the performing demodulation according to the symbol probability, and outputting demodulation information comprises: determining a maximum symbol probability of constellation points of which a bit to be calculated is 0 in the decision constellation point set as a probability that the bit to be calculated is 0; determining a maximum symbol probability of constellation points of which a bit to be calculated is 1 in the decision constellation point set as a probability that the bit to be calculated is 1; and obtaining, according to the probability that the bit to be calculated is 0 and the probability that the bit to be calculated is 1, a likelihood ratio or a log-likelihood ratio of the bit to be calculated, and outputting the likelihood ratio or the log-likelihood ratio as the demodulation information; wherein the bit to be calculated is a certain bit in a data bit corresponding to a constellation point in the decision constellation point set.

5. The signal demodulation method according to claim 1 , wherein before the obtaining the symbol probability parameter, the method further comprising: determining a decision area in the modulation constellation graph, wherein a set of constellation points in the decision area is the decision constellation point set, and the constellation points in the decision area are a part of constellation points in the modulation constellation graph.

6. The signal demodulation method according to claim 5 , wherein the determining the decision area in the constellation graph comprises: determining a fan-shaped area or a square area comprising a corresponding location point of the receive signal in the constellation graph as the decision area.

7. A signal demodulation device, comprising: a parameter obtaining unit, configured to obtain a receive signal and a symbol probability parameter of the receive signal, wherein the symbol probability parameter comprises: amplitude r y and phase angle φ y of the receive signal, amplitude r x j and phase angle φ x j of each constellation point x j in a decision constellation point set, and a standard deviation σ n of Gaussian noise and a standard deviation σ θ of phase noise, wherein the decision constellation point set is located in a modulation constellation graph required for performing signal demodulation; a probability calculation unit, configured to calculate, according to the symbol probability parameter, a symbol probability that a transmit signal corresponding to the receive signal is each constellation point x j in the decision constellation point set, wherein the probability calculation unit is configured to calculate the symbol probability according to the following formula: Pr ⁡ ( x = x j / y ) = r y 4 ⁢ πσ n ⁢ exp ⁡ ( - ( r y - r x j ) 2 2 ⁢ σ n 2 - r x j ⁢ r y ⁡ ( φ y - φ x j ) 2 2 ⁢ ⁢ v j ) / v j wherein the v j =r x j r y σ θ 2 +σ n 2 , and the Pr(x=x j /y) is the symbol probability; and a demodulation processing unit, configured to perform demodulation according to the symbol probability, and output demodulation information, wherein the demodulation information corresponds to a data bit corresponding to the transmit signal.

8. The signal demodulation device according to claim 7 , wherein the demodulation processing unit comprises: a constellation decision subunit, configured to determine that a constellation point having a maximum symbol probability in the decision constellation point set is a constellation point corresponding to the transmit signal; and a bit mapping subunit, configured to search for a data bit corresponding to the constellation point, wherein the data bit is the data bit corresponding to the transmit signal, and output the data bit, wherein the data bit is the demodulation information.

9. The signal demodulation device according to claim 7 , wherein the demodulation processing unit is configured to perform the demodulation according to the symbol probability, and output soft information used to generate the data bit corresponding to the transmit signal, wherein the soft information comprises a symbol probability, a bit probability, a likelihood ratio, or a log-likelihood ratio, and wherein the soft information is the demodulation information.

10. The signal demodulation device according to claim 9 , wherein the demodulation processing unit comprises: a bit probability subunit, configured to determine a maximum symbol probability of constellation points of which a bit to be calculated is 0 in the decision constellation point set as a probability that the bit to be calculated is 0, and determine a maximum symbol probability of constellation points of which a bit to be calculated is 1 in the decision constellation point set as a probability that the bit to be calculated is 1; and an information processing subunit, configured to obtain, according to the probability that the bit to be calculated is 0 and the probability that the bit to be calculated is 1, a likelihood ratio or a log-likelihood ratio of the bit to be calculated, and output the likelihood ratio or the log-likelihood ratio as the demodulation information, wherein the bit to be calculated is a certain bit in a data bit corresponding to a constellation point in the decision constellation point set.

11. The signal demodulation device according to claim 7 , further comprising: a decision area determination unit, configured to determine a decision area in the modulation constellation graph, wherein a set of constellation points in the decision area is the decision constellation point set, and the constellation points in the decision area are a part of constellation points in the modulation constellation graph.